JP6794501B2 - Absolute encoder - Google Patents

Description

The present invention relates to an absolute encoder for specifying the amount of rotation of an input shaft.

Conventionally, rotary encoders used for detecting the positions and angles of moving elements in various control mechanical devices are known. Such encoders include incremental encoders that detect relative positions or angles, and absolute encoders that detect absolute positions or angles. For example, Patent Document 1 describes an absolute type for digitally measuring the amount of rotation of a rotary shaft for motion control of an automatic control device or a robot device, a rotary shaft for power transmission used for opening and closing a valve, or the like as an absolute amount. The rotary encoder is described.

Jikkenhei 4-96019

The absolute encoder described in Patent Document 1 has a configuration in which a 1-bit rotation sensor is attached to the rotation shaft of each of the gears connected in multiple stages. Each of these gears sequentially decelerates and rotates to form a 1-bit counter. In such an encoder, if the number of counters is reduced, the resolution is lowered. Therefore, if the number of counters is increased in order to secure the resolution, there is a problem that the encoder becomes large.

The present invention has been made in view of such a problem, and an object of the present invention is to provide an absolute encoder capable of suppressing an increase in size while ensuring resolution.

In order to solve the above problems, the absolute encoder according to an embodiment of the present invention is an absolute encoder that specifies the amount of rotation over a plurality of rotations of the spindle, and includes a rotating body that rotates with the rotation of the spindle and a rotating body. It includes a magnet that rotates integrally, and a plurality of rotation sensors that detect the magnetic poles of the magnet and output sinusoidal detection signals having different phases.

According to this aspect, in the absolute encoder, it is possible to specify the amount of rotation over a plurality of rotations of the spindle according to the sinusoidal detection signals of different phases of the rotation sensor.

Another aspect of the invention is also an absolute encoder. This absolute encoder is an absolute encoder that specifies the amount of rotation over a plurality of rotations of the main shaft, and includes a first acquisition mechanism that acquires the rotation angle of the first rotating body that rotates integrally with the main shaft, and a first rotating body. On the other hand, the second acquisition mechanism that acquires the rotation angle of the second rotating body that decelerates and rotates at the first reduction ratio and the magnetic pole of the magnet that decelerates and rotates at the second reduction ratio with respect to the second rotating body are detected and respectively. A third acquisition mechanism that acquires a plurality of sinusoidal detection signals having different phases, and a first specific element that specifies the rotation speed of the first rotating body according to the acquired rotation angle and detection signal of the second rotating body. And a second specific element that specifies the amount of rotation of the spindle according to the acquired rotation angle of the first rotating body and the specified rotation number of the first rotating body.

Yet another aspect of the present invention is a method of specifying the amount of rotation. This method is a method of specifying the amount of rotation over a plurality of rotations of the main shaft, and obtains the rotation angle of the first rotating body that rotates integrally with the main shaft, and first decelerates the first rotating body. Acquiring the rotation angle of the second rotating body that decelerates and rotates at the ratio, and detecting the magnetic poles of the magnet that decelerates and rotates at the second reduction ratio with respect to the second rotating body, each of which has a plurality of sinusoidal shapes having different phases. Acquiring the detection signal, specifying the rotation number of the first rotating body according to the acquired rotation angle of the second rotating body and the detection signal, and specifying the rotation angle of the acquired first rotating body. Includes specifying the amount of rotation of the spindle according to the number of rotations of the first rotating body.

It should be noted that any combination of the above components or components and expressions of the present invention that are mutually replaced between methods, devices, systems, and the like are also effective as aspects of the present invention.

According to the present invention, it is possible to provide an absolute encoder capable of suppressing an increase in size while ensuring resolution.

It is a perspective view which shows the encoder which concerns on embodiment. It is a block diagram explaining the encoder of FIG. It is a development view explaining the encoder of FIG. It is a perspective view which shows the part of the encoder of FIG. 1 enlarged. It is another perspective view which shows a part of the encoder of FIG. 1 enlarged. It is explanatory drawing explaining the operation of the correspondence table of the encoder of FIG. It is a front view which shows the part of the encoder of FIG. 1 enlarged. It is a rear view which shows the part of the encoder of FIG. 1 enlarged. It is a top view which shows the part of the encoder of FIG. 1 enlarged. It is sectional drawing which shows the periphery of the 1st rotating body and the intermediate rotating body. It is sectional drawing which shows the periphery of the 2nd rotating body. It is a front view which shows the periphery of a Hall element. It is sectional drawing which shows the periphery of the 1st rotating body, the intermediate rotating body, and the 3rd rotating body. It is a developed view explaining the encoder of the 1st modification. It is explanatory drawing explaining the operation of the correspondence table of the encoder of the 1st modification.

The present inventor has obtained the following recognition about an absolute encoder (hereinafter, simply referred to as an encoder). As the encoder, for example, it is conceivable to configure a plurality of angle sensors that detect the absolute rotation angle within one rotation of the spindle and output it as a digital signal. As an example of an encoder in which a plurality of angle sensors are combined, a configuration in which separate angle sensors are provided for each of the three axes of the first slave axis and the second slave axis that rotate at a reduction ratio different from that of the main axis can be considered. In this configuration, the amount of rotation over a plurality of rotations of the spindle is digitally calculated based on the rotation angles detected from the three axes of the spindle, the first slave axis, and the second slave axis. The digital calculation includes, for example, the calculation by the amount converted into the N-ary system. In this configuration, the amount of rotation is calculated from the angle of rotation. Therefore, if the resolution of any of the angles of rotation detected by a plurality of angle sensors (hereinafter referred to as the detected angle of rotation) is low, the accuracy of the calculated amount of rotation will be high. There is a problem of decreasing. In order to improve this accuracy, it is conceivable to attach high-resolution angle sensors to all three axes, but in this case, there is a problem that providing three expensive angle sensors is disadvantageous in cost reduction.

Further, in this configuration, the rotation angle (digital signal) detected by each of these three angle sensors is calculated by the CPU (central processing unit) using a complicated algorithm to obtain the rotation amount. Therefore, if a CPU having a low computing power is used, there is a concern that the computing may not catch up and malfunction. From this, the inventor recognized that there is room for improvement in the configuration in which a plurality of rotation angles are processed in parallel to specify the rotation amount from the viewpoint of improving accuracy while suppressing cost increase.

Based on these, the inventor determines the amount of rotation over a plurality of rotations of the spindle (hereinafter referred to as multiple rotations) based on the angle of rotation within one rotation of the spindle and the number of rotations which is the number of rotations of the spindle. Found that it can be identified by.
(Equation 1) Spindle rotation amount = Spindle rotation angle + Spindle rotation speed x 360 °
By specifying the amount of rotation of the spindle in this way, it is possible to provide an absolute encoder capable of maintaining accuracy while suppressing cost increase.
The embodiment was devised based on such thoughts, and a specific configuration will be described below.

Hereinafter, the present invention will be described with reference to each drawing based on a preferred embodiment. In the embodiments and modifications, the same or equivalent components and members are designated by the same reference numerals, and redundant description will be omitted as appropriate. In addition, the dimensions of the members in each drawing are shown enlarged or reduced as appropriate for easy understanding. In addition, some of the members that are not important for explaining the embodiment in each drawing are omitted and displayed.
Also, terms including ordinal numbers such as 1st and 2nd are used to describe various components, but this term is used only for the purpose of distinguishing one component from other components. The components are not limited by.

[Embodiment]
The encoder 100 according to the embodiment of the present invention will be described. FIG. 1 is a perspective view showing an encoder 100 according to an embodiment. Hereinafter, the description will be given based on the XYZ Cartesian coordinate system. The X-axis direction corresponds to the horizontal front-back direction, the Y-axis direction corresponds to the horizontal left-right direction, and the Z-axis direction corresponds to the vertical vertical direction. The Y-axis direction and the Z-axis direction are orthogonal to the X-axis direction, respectively. The X-axis direction may be described as forward or backward, the Y-axis direction may be described as left or right, and the Z-axis direction may be described as upward or downward. The notation in such a direction does not limit the usage posture of the encoder 100, and the encoder 100 can be used in any posture.

The encoder 100 is an absolute encoder that specifies and outputs the amount of rotation of the spindle 1a of the motor 1 over a plurality of rotations. As an example, the motor 1 may be a stepping motor or a DC brushless motor. As an example, the motor 1 may be applied as a drive source for driving a robot for industrial use or the like via a reduction mechanism such as a wave gearing device. The encoder 100 outputs the amount of rotation of the specified spindle 1a as a digital signal. FIG. 2 is a block diagram illustrating the encoder 100. FIG. 3 is a developed view illustrating the encoder 100. FIG. 4 is an enlarged perspective view showing a part of the encoder 100. FIG. 5 is another perspective view showing a part of the encoder 100 in an enlarged manner.

As shown in FIG. 2, the encoder 100 includes a spindle 1a, a first rotating body 20, an intermediate rotating body 22, a second rotating body 24, a third rotating body 26, an angle sensor AS1, and an angle sensor AS2. A magnet M1, a magnet M2, a magnet M3, a plurality of rotation sensors 38, and a control unit 40 are included.

The spindle 1a is an output shaft of the motor 1 and is an input shaft to which rotation is input to the encoder 100. The first rotating body 20 is fixed to the spindle 1a and is rotatably supported by the bearing member of the motor 1 integrally with the spindle 1a. The intermediate rotating body 22, the second rotating body 24, and the third rotating body 26 are rotatably supported by a shaft described later. The intermediate rotating body 22 is driven by the first rotating body 20 via the first deceleration mechanism 21 and decelerates and rotates with respect to the first rotating body 20 at a reduction ratio R1. The second rotating body 24 is driven by the intermediate rotating body 22 via the worm mechanism 15 and decelerates and rotates with respect to the intermediate rotating body 22 at a reduction ratio R2. Assuming that the product of the reduction ratio R1 and the reduction ratio R2 is the reduction ratio R12, the second rotating body 24 decelerates and rotates at the reduction ratio R12 with respect to the first rotating body 20. As an example, the reduction ratio R1 may be 1/2, the reduction ratio R2 may be 1/50, and the reduction ratio R12 may be 1/100. These reduction ratios may be set according to the resolution of the encoder 100. When the first rotating body 20 rotates 100 times, the second rotating body 24 makes one rotation.

The third rotating body 26 is driven by the second rotating body 24 via the second deceleration mechanism 25, and decelerates and rotates with respect to the second rotating body 24 at a reduction ratio R23. As an example, the reduction ratio R23 may be 1/4. When the second rotating body 24 makes four rotations, the third rotating body 26 makes one rotation. The third rotating body 26 decelerates and rotates at a reduction ratio (= 1/400) obtained by multiplying the reduction ratio R12 by the reduction ratio R23 with respect to the first rotating body 20. When the first rotating body 20 rotates 400 times, the third rotating body 26 makes one rotation. That is, by specifying the rotation position of the third rotating body 26 during one rotation, the absolute rotation amount of 400 rotations (± 200 rotations) of the first rotating body 20 can be specified.

The magnet M1 has a two-pole magnetic pole P1 on an end surface facing the angle sensor AS1 in the rotation axis direction of the first rotating body 20. The magnet M1 rotates integrally with the first rotating body 20. The angle sensor AS1 detects the rotation angle (= rotation angle of the spindle 1a) of the first rotating body 20 according to the magnetic flux density received from the magnetic pole P1.

The magnet M2 has a two-pole magnetic pole P2 on an end surface facing the angle sensor AS2 in the rotation axis direction of the second rotating body 24. The magnet M2 rotates integrally with the second rotating body 24. The angle sensor AS2 detects the rotation angle of the second rotating body 24 according to the magnetic flux density received from the magnetic pole P2.

The plurality of rotation sensors 38 include Hall elements H1 and H2 (hereinafter, may be referred to as Hall elements). Each Hall element may include a thin film of a compound semiconductor such as gallium arsenide (GaAs) or indium antimonide (InSb) or a single element semiconductor such as silicon (Si). The magnet M3 has a two-pole magnetic pole P3 on an end face facing each Hall element in the axial direction of the third rotating body 26. The Hall elements H1 and H2 are arranged at positions separated by π / 2 by the electric angle. When the magnet M3 rotates integrally with the third rotating body 26, the Hall element H1 and the Hall element H2 output a sinusoidal detection signal having a phase difference of 90 °. The sinusoidal signal refers to a wavy signal whose amplitude gradually changes with time regardless of its name, and does not include a rectangular wavy signal whose amplitude changes steeply or discontinuously. The sinusoidal signal includes a signal containing harmonics that do not substantially affect the accuracy of the encoder, such as a signal called a triangular wave.

The control unit 40 determines the rotation angle of the first rotating body 20 detected by the angle sensor AS1, the rotation angle of the second rotating body 24 detected by the angle sensor AS2, and the detection signals from the Hall elements H1 and H2. get. The control unit 40 specifies the rotation speed of the second rotating body 24 with reference to the correspondence table 44 according to the acquired detection signals from the Hall elements H1 and H2. The control unit 40 specifies the rotation speed of the first rotating body 20 from the acquired rotation angle of the second rotating body 24 and the rotation speed of the specified second rotating body 24. The rotation speed of the first rotating body 20 can be specified by, for example, Equation 2.
(Equation 2) Rotation speed of the first rotating body 20 = rotation angle of the second rotating body 24 / (R12 × 360) + rotation speed of the second rotating body 24 / R12

The control unit 40 specifies the amount of rotation of the first rotating body 20 from the specified rotation speed of the first rotating body 20 and the acquired rotation angle of the first rotating body 20. The amount of rotation of the first rotating body 20 can be specified by, for example, Equation 3.
(Equation 3) Rotation amount of the first rotating body 20 = rotation angle of the first rotating body 20 + rotation speed of the first rotating body 20 × 360 °
Since the amount of rotation of the spindle 1a is equal to the amount of rotation of the first rotating body 20, the amount of rotation of the spindle 1a can be specified by, for example, Equation 4.
(Equation 4) Rotation amount of spindle 1a = rotation angle of first rotating body 20 + rotation speed of first rotating body 20 × 360 °

Subsequently, each element of the encoder 100 will be described.

(Control unit)
As shown in FIG. 2, the control unit 40 includes a first rotation angle acquisition unit 41, a second rotation angle acquisition unit 42, a hall signal acquisition unit 43, a correspondence table 44, and a rotation speed specifying unit 45. The output unit 46 and the like are included. Each of these blocks can be realized by elements and mechanical devices such as the CPU (central processing unit) of a computer in terms of hardware, and by a computer program or the like in terms of software. It depicts a functional block realized by cooperation. Therefore, it will be understood by those skilled in the art who have referred to this specification that these functional blocks can be realized in various forms by combining hardware and software.

The first rotation angle acquisition unit 41 acquires the rotation angle of the first rotating body 20 detected by the angle sensor AS1. The second rotation angle acquisition unit 42 acquires the rotation angle of the second rotating body 24 detected by the angle sensor AS2. The Hall signal acquisition unit 43 acquires sinusoidal detection signals from the Hall elements H1 and H2. The Hall signal acquisition unit 43 includes, for example, an AD converter, and converts the detection signals from the Hall elements H1 and H2, which are analog signals, into digital detection signals and acquires them.

(Correspondence table)
FIG. 6 is an explanatory diagram illustrating an example of the operation of the correspondence table 44. The correspondence table 44 shows, for example, information on the amplitudes of two sinusoidal signals Ha and Hb having a phase difference of 90 °, an angle θ corresponding to the amplitudes of the two signals, and a second angle θ corresponding to the angles θ. The number of rotations N2 of the rotating body 24 and the number N2 are stored in a table format. The correspondence table 44 specifies the angle θ in the range of 0 ° to 360 ° corresponding to the amplitude of the acquired digital detection signal. The correspondence table 44 specifies the rotation speed N2 of the second rotating body 24 in the range of 0 to 3 rotations corresponding to the specified angle θ. As shown in FIG. 6, N2 = 0 rotation in the range where the angle θ is 0 ° or more and less than 90 °, N2 = 1 rotation in the range where the angle θ is 90 ° or more and less than 180 °, and the angle θ is 180 ° or more. In the range of less than 270 °, N2 = 2 rotations, and in the range of the angle θ of 270 ° or more and less than 360 °, N2 = 3 rotations are specified.

For example, assume that the angle θ is unknown, the amplitude of the signal Ha is 0.87, and the amplitude of the signal Ha is −0.5. There are two angles θ in which the amplitude of the signal Ha is 0.87, 60 ° (A1) and 120 ° (A2). Of these, the angle θ in which the amplitude of the signal Hb is −0.5 is specified only at 120 ° (B2), and the angle θ = 60 ° (B1) in which the amplitude is 0.5 is denied. Since the specified angle θ = 120 ° belongs to the range of 90 ° or more and less than 180 °, the rotation speed N2 of the second rotating body 24 is specified as one rotation. In this way, by tabulating and using the angle and amplitude information of the sinusoidal signals having a plurality of phases, the angle can be specified from the amplitude information. Further, the rotation speed N2 of the second rotating body 24 can be specified from the angle.

The rotation speed specifying unit 45 is based on the rotation speed of the second rotating body 24 acquired by the second rotation angle acquiring unit 42 and the rotation speed N2 of the second rotating body 24 specified with reference to the correspondence table 44. The rotation speed of the first rotating body 20 is specified by the above equation 2. The output unit 46 is based on the above equation 4 from the rotation angle of the first rotating body 20 acquired by the first rotation angle acquisition unit 41 and the rotation speed of the first rotating body 20 specified by the rotation speed specifying unit 45. The amount of rotation of the spindle 1a is specified and output.

(magnet)
The magnets M1 to M3 (hereinafter, may be referred to as each magnet) have a substantially cylindrical shape. Each magnet is formed of, for example, a ferrite-based or NdFeB-based magnet material. Each magnet may be, for example, a rubber magnet containing a resin binder or a bond magnet. A plurality of (for example, two poles) magnetic poles are provided on the facing surface of each magnet facing each angle sensor. The magnetizing direction of each magnet may be a direction orthogonal to the facing surface of each magnet, or may be a direction parallel to the facing surface. The direction may be parallel to the facing surface inside each magnet and orthogonal to the facing surface in the vicinity of the facing surface. In the embodiment, a two-pole magnetic pole is provided at the end of each magnet facing each angle sensor.

Each magnet is housed in a recess formed in a magnet holder provided at the end of each rotor toward each angle sensor, and may be fixed by, for example, adhesion or caulking. A magnetic pole is formed in each magnet by magnetism. The magnetic flux density distribution in the rotation direction of each magnet may have a trapezoidal wave shape, a sinusoidal wave shape, or a square wave shape. In the embodiment, it is magnetized in a trapezoidal wavy shape. By adjusting the distance from each magnet to the angle sensors AS1 and AS2 and the plurality of rotation sensors 38 (hereinafter referred to as each detection element), the distribution of the magnetic flux density received by each detection element can be changed. In the embodiment, the position of each magnet is set so that the distribution of the magnetic flux density received by each detection element is sinusoidal. For example, when the magnet M3 is continuously rotated, the plurality of rotation sensors 38 output detection signals that change in a sinusoidal shape.

(Angle sensor)
The angle sensors AS1 and AS2 (hereinafter, may be referred to as each angle sensor) are sensors that detect an absolute rotation angle in the range of 0 ° to 360 ° corresponding to one rotation of each rotor. Each angle sensor outputs a signal (for example, a digital signal) corresponding to the detected angle of rotation to the control unit 40. Each angle sensor outputs the same angle of rotation as before the energization was stopped, even when the energization was once stopped and then re-energized. Therefore, a configuration without a backup power supply is possible. As shown in FIG. 4, the angle sensor AS1 is fixed to the sensor support portion at a position facing the magnetic pole of the magnet M1 provided on the axial end surface of the first rotating body 20 via a gap. The angle sensor AS2 is fixed to the sensor support portion at a position facing the magnetic pole of the magnet M2 provided on the axial end surface of the second rotating body 24 via a gap.

A magnetic angle sensor having a relatively high resolution may be used for each angle sensor. The magnetic angle sensors are arranged to face each other in the axial direction of each rotating body, for example, with the two poles of the magnet via a gap, and the rotation angle of the rotor is specified based on the rotation of these magnetic poles to output a digital signal. To do. As an example, the magnetic angle sensor includes a detection element that detects a magnetic pole and an arithmetic circuit that outputs a digital signal based on the output of the detection element. The detection element may include a plurality of (for example, four) magnetic field detection elements such as a Hall element and a GMR (Giant Magneto Resistive) element. The arithmetic circuit may specify the rotation angle by table processing using a look-up table, for example, using the difference or ratio of the outputs of a plurality of detection elements as a key. The detection element and the arithmetic circuit may be integrated on one IC chip. This IC chip may be embedded in a resin having a thin rectangular parallelepiped outer shape. Each angle sensor outputs an angle signal, which is a digital signal corresponding to the rotation angle of each rotor detected via a wiring member (not shown), to the control unit 40.

In particular, the angle sensor AS1 detects the magnetic pole of the magnet M1 provided on the first rotating body 20 and outputs the rotation angle of the first rotating body 20 as a digital signal of a plurality of bits (for example, 7 bits). The angle sensor AS2 detects the magnetic pole of the magnet M2 provided on the second rotating body 24 and outputs the rotation angle of the second rotating body 24 as a digital signal of a plurality of bits (for example, 7 bits).

Subsequently, with reference to FIGS. 7 to 13, the first rotating body 20, the intermediate rotating body 22, the second rotating body 24 and the third rotating body 26 (hereinafter referred to as each rotating body) of the encoder 100 and their peripheral configurations are configured. To explain. FIG. 7 is a front view of the encoder 100. FIG. 8 is a rear view of the encoder 100. FIG. 9 is a plan view of the encoder 100. FIG. 9 omits the illustration of members such as the bracket 10 and the angle sensor AS1, which will be described later. FIG. 10 is a partial cross-sectional view showing the periphery of the first rotating body 20 and the intermediate rotating body 22. FIG. 11 is a partial cross-sectional view showing the periphery of the second rotating body 24. FIG. 12 is a front view showing the periphery of the Hall elements H1 and H2. FIG. 12 omits the illustration of members such as the bracket 18 and the bracket 7, which will be described later from FIG. FIG. 13 is a partial cross-sectional view showing the periphery of the first rotating body 20, the intermediate rotating body 22, and the third rotating body 26. Each rotating body and its peripheral members are supported by a disk-shaped base 2 fixed to the upper side of the motor 1.

The first rotating body 20 includes a circular member 3 and a magnet M1. The circular member 3 extends in the Z-axis direction and has a magnet holder 3h and a drive gear 3d in this order from the side closer to the angle sensor AS1 (see particularly FIG. 10). A recess 3k is formed on the end surface of the magnet holder 3h facing the angle sensor AS1. The recess 3k has a shape of being recessed in a circle in the direction of the rotation axis of the first rotating body 20. The recess 3k of the magnet holder 3h accommodates and fixes the magnet M1. The drive gear 3d is a spur gear having 24 gear teeth at positions whose outer circumference is divided into 24 equal parts. A hole 3j into which the main shaft 1a is inserted and fixed is formed at the end of the circular member 3 on the motor 1 side.

The intermediate rotating body 22 is an element that decelerates and transmits rotation between the first rotating body 20 and the second rotating body 24. By providing the intermediate rotating body 22, the reduction ratio R12 between the first rotating body 20 and the second rotating body 24 can be increased. The rotation axis of the intermediate rotating body 22 is provided so as to extend in the Z-axis direction in parallel with the rotation axis of the first rotating body 20. The intermediate rotating body 22 includes a circular member 5 on which a driven gear 5e and a worm gear portion 5w are formed on the outer peripheral surface (particularly see FIG. 10). The circular member 5 extends in the Z-axis direction. The circular member 5 has a hole 5j in which the shaft 5s fixed by the nut 5n is accommodated in the base 2, and is rotatably supported by the shaft 5s. The driven gear 5e meshes with the driving gear 3d and is driven by the driving gear 3d. The driven gear 5e and the driving gear 3d constitute the first reduction mechanism 21 (see particularly FIG. 9). The driven gear 5e is a spur gear having 48 gear teeth at positions whose outer circumference is divided into 48 equal parts. The worm gear portion 5w is a cylindrical worm extending upward from the driven gear 5e. For example, one thread-shaped groove is provided on the outer peripheral surface of the worm gear portion 5w. The screw-shaped groove may have a plurality of threads.

When the worm gear portion 5w rotates, an upward force may act on the circular member 5 due to the action of the worm. Therefore, in the embodiment, a worm pressing portion 19a for pressing the hemispherical protrusion 5c provided at the upper end of the circular member 5 is provided (particularly see FIG. 7). The worm pressing portion 19a abuts on the hemispherical protrusion 5c and presses it downward to suppress the movement of the circular member 5. The worm holding portion 19a is provided on the other end side of the angle-shaped leaf spring 19 whose one end is fixed to the bracket 10. The leaf spring 19 is fixed to the bracket 10 by, for example, a rivet or a screw. The bracket 10 will be described later. As an example, the leaf spring 19 may be formed of a stainless steel plate having a plate thickness of about 0.1 mm to 0.2 mm.

The second rotating body 24 includes a circular member 6 and a magnet M2. The circular member 6 extends in the Y-axis direction (see particularly FIG. 11). The circular member 6 is formed with a magnet holder 6h, a worm wheel portion 6w, and a drive gear 6d in this order from the side closer to the angle sensor AS2. The magnet holder 6h has a recess 6k formed on the end surface facing the angle sensor AS2. The recess 6k has a shape of being recessed in a circle in the rotation axis direction of the second rotating body 24. The recess 6k of the magnet holder 6h accommodates and fixes the magnet M2. The circular member 6 has a hole 6j for accommodating the shaft 6s and is rotatably supported by the shaft 6s. The shaft 6s is fixed to a portion of the bracket 7 extending upward from the base 2 by a nut 6n. The bracket 7 is formed by cutting a part of the base 2 upward. The bracket 7 may be formed separately from the base 2. The bracket 7 may be, for example, an angle-shaped member whose one end is fixed to the base 2. The shaft 6s extends in the Y-axis direction parallel to the base 2.

The worm wheel portion 6w meshes with the worm gear portion 5w of the intermediate rotating body 22 and is driven by the worm gear portion 5w. The worm wheel portion 6w has 50 gear teeth at positions where the outer circumference thereof is divided into 50 equal parts. The gear teeth of the worm wheel portion 6w may be oblique gears. The worm gear portion 5w and the worm wheel portion 6w form a worm mechanism 15 (see particularly FIG. 9). The drive gear 6d is a spur gear having 15 gear teeth at positions whose outer circumference is divided into 15 equal parts. The rotation axis of the second rotating body 24 is provided so as to be inclined by 90 ° from the rotation axis of the first rotating body 20 and the intermediate rotating body 22.

The third rotating body 26 includes a circular member 8 and a magnet M3 (see particularly FIG. 13). The circular member 8 extends in the Y-axis direction. A magnet holder 8h and a driven gear 8e are formed on the circular member 8 in this order from the side closer to the Hall elements H1 and H1. The magnet holder 8h is formed with recesses 8k on the end faces facing the Hall elements H1 and H1. The recess 8k has a shape of being recessed in a circle in the rotation axis direction of the third rotating body 26. The recess 8k of the magnet holder 8h accommodates and fixes the magnet M3. The circular member 8 has a hole 8j for accommodating the shaft 8s, and is rotatably supported by the shaft 8s. The shaft 8s is fixed to a portion of the bracket 9 extending upward from the base 2 by caulking or the like. The bracket 9 is formed by cutting a part of the base 2 upward. The bracket 9 may be formed separately from the base 2. The bracket 9 may be, for example, an angle-shaped member whose one end is fixed to the base 2. The shaft 8s extends in the Y-axis direction parallel to the base 2. The driven gear 8e is a spur gear having 60 gear teeth at positions whose outer circumference is divided into 60 equal parts. The driven gear 8e meshes with the driving gear 6d and is driven by the driving gear 6d. The driven gear 8e and the driving gear 6d constitute a second reduction gear mechanism 25 (see particularly FIG. 9). The rotation axis of the third rotating body 26 is provided parallel to the rotation axis of the second rotating body 24.

Subsequently, the first sensor support portion 11, the second sensor support portion 14, and the Hall element support portion 17 will be described (see particularly FIGS. 4, 5, 7, and 13). The first sensor support portion 11 includes a bracket 10 and a sensor holder 13. The second sensor support portion 14 includes a bracket 12 and a sensor holder 16. The Hall element support portion 17 includes a bracket 18. The brackets 10, 12, and 18 are angle-shaped members, one end of which is fixed to the base 2 by, for example, rivets or screws. The sensor holders 13 and 16 have a protrusion that fits into a support hole formed on the other end side of the brackets 10 and 12, and an accommodating portion that accommodates the angle sensors AS1 and AS2.

The Hall elements H1 and H2 are supported on the other end side of the bracket 18. The Hall elements H1 and H2 are arranged so that their centers are located in the vicinity of the contour line of the magnet M3 (see particularly FIGS. 5, 8 and 12). As an example, the Hall element H1 is arranged at the 12 o'clock position and the Hall element H2 is arranged at the 9 o'clock position.

The circular members 3, 5, 6 and 8 may be formed by molding from a resin material such as polyacetal. The shafts 5s, 6s, and 8s may be formed from, for example, stainless steel rods by cutting, grinding, rolling, or forging. The base 2 and the brackets 7, 9, 10, 12, and 18 may be formed by press working from, for example, a stainless steel plate having a thickness of about 1 mm. A wet lubrication method in which grease or the like is applied may be used for lubrication of each gear portion, but in the embodiment, a dry lubrication method is adopted.

Subsequently, the features of the encoder 100 will be described.
It is desirable that the encoder has an inexpensive configuration and can increase the resolution. Therefore, the encoder 100 of the embodiment includes a magnet M3 that rotates integrally with the rotating body, a plurality of rotation sensors 38 that detect the magnetic poles P3 of the magnet M3, and output sinusoidal detection signals having different phases. To be equipped with. According to this configuration, since the encoder 100 specifies the rotation amount of the spindle 1a by using the sinusoidal detection signals of different phases of the plurality of rotation sensors 38, the resolution can be improved with an inexpensive configuration.

From the viewpoint of miniaturization, it is desirable that the number of angle sensors is small. Therefore, in the encoder 100 of the embodiment, the rotating body includes a first rotating body 20 that rotates integrally with the main shaft 1a and a third rotating body 26 that rotates with the rotation of the first rotating body 20. An angle sensor AS1 for detecting the rotation angle of the one rotating body 20 is provided, and the magnet M3 is arranged on the third rotating body 26. According to this configuration, the rotation amount of the spindle 1a can be specified by using the rotation angle of the first rotating body 20 detected by the angle sensor AS1 and the detection signal of the rotation sensor 38, so that even if the number of angle sensors is reduced. , The desired resolution can be easily obtained.

The encoder should be small. Therefore, in the encoder 100 of the embodiment, the rotating body includes the second rotating body 24 arranged between the first rotating body 20 and the third rotating body 26, and detects the rotation angle of the second rotating body 24. The second rotating body 24 is provided with the angle sensor AS2 and decelerates and rotates with respect to the first rotating body 20 at a reduction ratio R12, and the third rotating body 26 decelerates and rotates with respect to the second rotating body 24 with a reduction ratio R23. To do. According to this configuration, the number of rotating bodies and the number of angle sensors can be reduced, which is advantageous for miniaturization of the encoder 100. The encoder 100 can be configured so that the projection range in which the encoder 100 is projected in the Z-axis direction falls within the range in which the motor 1 is projected in the Z-axis direction. As an example, the projection range of the encoder 100 in the Z-axis direction may be set to fit inside a square having a side of 42 mm or a circle having a diameter of 42 mm.

In an encoder that calculates the amount of rotation by high-level calculation using a large number of angle sensors, there is a concern that the calculation speed cannot keep up with the high-speed rotation and malfunction. Therefore, in the encoder 100 of the embodiment, the rotation angle of the first rotating body 20 is specified according to the detection result of the angle sensor AS1, and according to the detection result of the angle sensor AS2 and the detection signals from the plurality of rotation sensors 38. The rotation number of the first rotating body 20 is specified, and the rotation amount of the first rotating body 20 is specified according to the rotation angle of the specified first rotating body 20 and the rotation number of the first rotating body 20. According to this configuration, since the amount of processing for specifying the amount of rotation is small, it is possible to reduce malfunctions when rotating at high speed. Since the amount of processing is small, it is possible to adopt a relatively low-speed CPU for the control device, and it is possible to suppress an increase in power consumption. It is advantageous for cost reduction because the number of expensive angle sensors can be reduced.

When the rotation direction is reversed, it is considered that the error of the detected rotation angle increases due to the backlash of the gear of the transmission mechanism. Therefore, in the encoder 100 of the embodiment, the mechanism for transmitting the rotation of the first rotating body 20 to the second rotating body 24 includes a worm mechanism 15 including a worm gear portion 5w and a worm wheel portion 6w. According to this configuration, backlash can be suppressed and the error of the rotation angle can be reduced. In particular, even if the reduction ratio R12 between the first rotating body 20 and the second rotating body 24 is set high, the occurrence of an error can be suppressed.

In the configuration in which the worm gear is provided on the first rotating body 20, it is desirable to press the end portion of the first rotating body 20, and in this case, it becomes difficult to arrange the angle sensor AS1 near the end portion of the first rotating body 20. Therefore, in the encoder 100 of the embodiment, the mechanism for transmitting the rotation of the first rotating body 20 to the second rotating body 24 decelerates and rotates at a reduction ratio R1 (for example, 1/2) with respect to the first rotating body 20. The second rotating body 24 includes the intermediate rotating body 22 and decelerates and rotates at a reduction ratio R2 (for example, 1/50) with respect to the intermediate rotating body 22. According to this configuration, the worm gear portion 5w can be formed on the intermediate rotating body 22 and the worm holding portion 19a can be brought into contact with the end portion thereof. It becomes easy to arrange.

If the worm mechanism is rotated at high speed, the durability may decrease. Therefore, in the encoder 100 of the embodiment, the worm gear portion 5w is provided on the intermediate rotating body 22. According to this configuration, since the worm gear portion 5w is formed on the intermediate rotating body 22 that rotates at a lower speed than the first rotating body 20, the rotating speed of the worm mechanism 15 can be reduced and the durability can be improved.

When the worm gear portion 5w rotates, a force in the rotation axis direction acts on the intermediate rotating body 22, and the intermediate rotating body 22 may move in the rotation axis direction. Therefore, the encoder 100 of the embodiment includes a worm pressing portion 19a which is an urging member for urging the intermediate rotating body 22 so as to press the intermediate rotating body 22 in the rotation axis direction. According to this configuration, the movement of the intermediate rotating body 22 can be suppressed.

The encoder should be small. Therefore, in the encoder 100 of the embodiment, the rotation axis of the second rotating body 24 is provided parallel to the rotation axis of the third rotating body 26, and the first rotating body 20 is provided with the rotating axis of the second rotating body 24. It is provided so as to be sandwiched between the rotating shafts of the three rotating bodies 26. According to this configuration, since the second rotating body 24 and the third rotating body 26 can be arranged so as to surround the first rotating body 20, the encoder can be made more compact than the other configurations.

The detection accuracy of the sensor may decrease due to the interference of multiple magnetic fields. For example, if the magnetic field of the magnet M3 interferes with the magnetic field of the magnet M2, the detection accuracy of the angle sensor AS2 may decrease. Therefore, in the encoder 100 of the embodiment, the second rotating body 24 includes another magnet M2 that rotates integrally with the second rotating body 24, and the space is orthogonal to the rotation axis of the second rotating body 24. When the first rotating body 20 is divided into two regions by a plane including the rotation axis, another magnet M2 is arranged in the region of the two regions where the magnet M3 is not arranged. According to this configuration, since the magnet M3 is arranged in one region and the magnet M2 is arranged in the other region, the magnets are separated from each other and the deterioration of the detection accuracy of the angle sensor AS2 can be suppressed.
Each magnet may be arranged so that the direction of the magnetic field is different. As a result, it is possible to suppress a decrease in the detection accuracy of the angle sensor. In the encoder 100 of the embodiment, the magnets M1, M2, and M3 are arranged so that the directions of the magnetic fields are different from each other, but the direction of the magnetic field is only for the adjacent magnets in which the magnetic fields may interfere with each other. They may be arranged so as to face different directions.

If the encoder configuration becomes complicated, reliability may decrease. Therefore, the encoder 100 of the embodiment has a first acquisition mechanism (including a magnet M1, an angle sensor AS1 and a first rotation angle acquisition unit 41) that acquires the rotation angle of the first rotating body 20 that rotates integrally with the spindle 1a. The second acquisition mechanism (magnet M2, angle sensor AS2, and second rotation angle) that acquires the rotation angle of the second rotating body 24 that decelerates and rotates at a reduction ratio R12 (for example, 1/100) with respect to the first rotating body 20. (Including the acquisition unit 42) and the magnetic pole P3 of the magnet M3 that decelerates and rotates at a reduction ratio R23 (for example, 1/4) with respect to the second rotating body 24, and two sinusoidal detection signals having different phases. The number of rotations of the first rotating body 20 according to the acquired rotation angle of the second rotating body 24 and the detection signal, and the third acquisition mechanism (including the hall elements H1 and H2 and the hall signal acquiring unit 43). According to the first specific element (including the correspondence table 44 and the rotation number specifying unit 45), the acquired rotation angle of the first rotating body 20, and the rotation number of the specified first rotating body 20. A second specific element (including the output unit 46) that specifies the amount of rotation of the spindle 1a is provided. According to this configuration, since the number of elements for acquiring the rotation angle of the rotating body is small, the encoder configuration can be simplified and the decrease in reliability can be suppressed.

In the method of specifying the amount of rotation by high-level calculation, the processing of the CPU may become high speed and the power consumption may increase. Therefore, the method of specifying the amount of rotation applied to the encoder 100 of the embodiment is to acquire the rotation angle of the first rotating body 20 that rotates integrally with the main shaft 1a and to decelerate with respect to the first rotating body 20. Obtaining the rotation angle of the second rotating body 24 that decelerates and rotates at the ratio R12, and detecting the magnetic poles P3 of the magnet M3 that decelerates and rotates at the reduction ratio R23 with respect to the second rotating body 24, and a plurality of different phases. Acquiring the sinusoidal detection signal of the above, specifying the rotation speed of the first rotating body 20 according to the acquired rotation angle of the second rotating body and the detection signal, and acquiring the acquired first rotating body. Includes specifying the amount of rotation of the spindle 1a according to the angle of rotation of 20 and the number of rotations of the specified first rotating body 20. Since the amount of processing for specifying the amount of rotation can be reduced, a low-speed CPU can be adopted as the control device, and an increase in power consumption can be suppressed.

The above description has been made based on the embodiment of the present invention. These embodiments are exemplary, and it will be appreciated by those skilled in the art that various modifications and modifications are possible within the claims of the present invention, and that such modifications and modifications are also within the claims of the present invention. It is about to be understood. Therefore, the descriptions and drawings herein should be treated as exemplary rather than limiting.

Hereinafter, a modified example will be described. In the drawings and description of the modified examples, the same or equivalent components and members as those in the embodiment are designated by the same reference numerals. The description that overlaps with the embodiment will be omitted as appropriate, and the configuration different from the embodiment will be mainly described.

(First modification)
In the embodiment, an example in which the plurality of rotation sensors 38 include two Hall elements has been described, but the present invention is not limited to this. For example, the plurality of rotation sensors 38 may include three or more Hall elements.
In the embodiment, an example in which the intermediate rotating body 22 is provided and the worm gear portion 5w is formed on the intermediate rotating body 22 has been described, but the present invention is not limited to this. For example, the intermediate rotating body 22 may be deleted so that the worm gear portion is formed on the first rotating body 20. The encoder configuration becomes simpler, which is advantageous for miniaturization.

FIG. 14 is a development view for explaining the encoder 200 according to the first modification, and corresponds to FIG. The encoder 200 is different from the encoder 100 of the embodiment in a part described later, and other configurations are the same. In the encoder 200, the intermediate rotating body is deleted, and the worm gear portion 3w is formed in the first rotating body 20. The worm gear portion 3w and the worm wheel portion 6w form a worm mechanism 15. The encoder 200 includes three Hall elements H3, H4, and H5 instead of the Hall elements H1 and H2. The Hall elements H3, H4, and H5 are arranged at positions separated by 2π / 3 by the electric angle. The Hall elements H3, H4, and H5 each output three sinusoidal detection signals having a phase difference of 120 °. The Hall signal acquisition unit 43 converts the detection signals from the Hall elements H3, H4, and H5, which are analog signals, into digital detection signals and acquires them. The reduction ratio R23 of the third rotating body 26 with respect to the second rotating body 24 is set to 1/6. In the encoder 200 formed in this way, the third rotating body 26 makes one rotation when the second rotating body 24 makes six rotations, so that the third rotating body 26 makes one rotation when the first rotating body 20 makes 600 rotations. ..

FIG. 15 is an explanatory diagram illustrating an example of the operation of the correspondence table 44 in the encoder 200. FIG. 15 corresponds to FIG. In the correspondence table 44, the amplitudes of the three sinusoidal signals having a phase difference of 120 °, the angles θ corresponding to the amplitudes of the three signals, and the rotation of the second rotating body 24 corresponding to the angles θ. The number N2 and the number N2 are stored in a table format. The correspondence table 44 specifies the information of the angle θ in the range of 0 ° to 360 ° corresponding to the amplitude of the digital detection signal acquired by the Hall signal acquisition unit 43. The correspondence table 44 specifies the rotation speed N2 of the second rotating body 24 in the range of 0 to 5 rotations corresponding to the specified angle θ. As shown in FIG. 15, N2 = 0 rotations when the angle θ is 0 ° or more and less than 60 °, N2 = 1 rotation when the angle θ is 60 ° or more and less than 120 °, and the angle θ is 120 ° or more. N2 = 2 rotations in the range of less than 180 °, N2 = 3 rotations in the range of angle θ of 180 ° or more and less than 240 °, N2 = 4 rotations in the range of angle θ of 240 ° or more and less than 300 °, angle θ In the range of 300 ° or more and less than 350 °, N2 = 5 rotations is specified. By dividing one rotation of the third rotating body 26 into six parts and specifying them in this way, it is possible to specify each of the six rotations of the second rotating body 24. The encoder 200 configured in this way can specify the absolute rotation amount of 600 rotations (± 300 rotations) of the first rotating body 20.

(Second modification)
In the description of the embodiment, an example in which each of the magnets M1 to M3 is an integral member has been described, but the present invention is not limited to this. Each of the magnets M1 to M3 may be configured by combining a plurality of pieces.

(Third modification example)
In the description of the embodiment, an example in which the plurality of rotation sensors 38 are Hall elements has been described, but the present invention is not limited to this. The plurality of rotation sensors may be sensors based on another detection principle, as long as they detect the magnetic poles of the magnet and output a sinusoidal detection signal.

(Fourth modification)
In the description of the embodiment, an example in which the circular members 3, 5, 6 and 8 forming each gear are formed of a resin material has been described, but the present invention is not limited to this. Some of these circular members may be formed of metal or other materials.

According to the above-described modification, the same effect as that produced by the encoder 100 according to the embodiment is exhibited.

Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. The new embodiments resulting from the combination have the effects of the combined embodiments and variants.

100 ... Encoder, 1 ... Motor, 1a ... Main shaft, 20 ... 1st rotating body, 22 ... Intermediate rotating body, 24 ... 2nd rotating body, 26 ... 3rd rotating body, 38 ... Rotating Sensor, 40 ... Control unit, 200 ... Encoder, AS1 ... Angle sensor, AS2 ... Angle sensor, H1 ... Hall element, H2 ... Hall element, H3 ... Hall element, M1 ... Magnet, M2 ...・ Magnet, M3 ・ ・ Magnet.

Claims (2)

An absolute encoder that specifies the amount of rotation over multiple rotations of the spindle.
A rotating body that rotates with the rotation of the spindle,
A magnet that rotates integrally with the rotating body,
A plurality of rotation sensors that detect the magnetic poles of the magnet and output a detection signal,
With
The rotating body includes a first rotating body that rotates integrally with the main shaft, and a third rotating body that rotates with the rotation of the first rotating body.
A first angle sensor for detecting the rotation angle of the first rotating body is provided.
The magnet is arranged on the third rotating body and
The rotating body includes a second rotating body arranged between the first rotating body and the third rotating body.
The second rotating body decelerates and rotates at the first reduction ratio with respect to the first rotating body.
The third rotating body decelerates and rotates at a second reduction ratio with respect to the second rotating body.
The mechanism for transmitting the rotation of the first rotating body to the second rotating body includes a worm mechanism including a worm gear portion and a worm wheel portion.
The mechanism for transmitting the rotation of the first rotating body to the second rotating body includes an intermediate rotating body that decelerates and rotates at a third reduction ratio with respect to the first rotating body.
The second rotating body decelerates and rotates at the fourth reduction ratio with respect to the intermediate rotating body .
The rotation axis of the second rotating body is provided parallel to the rotation axis of the third rotating body.
The first rotating body, the absolute encoder according to claim Rukoto provided so as to be interposed between the rotary shaft of the third rotary member and the rotation axis of said second rotary member. The rotation angle of the first rotating body is specified according to the detection result of the first angle sensor.
A second angle sensor for detecting the rotation angle of the second rotating body is provided, and the rotation number of the first rotating body is specified according to the detection result of the second angle sensor and the detection signals from the plurality of rotation sensors. And
The absolute encoder according to claim 1, wherein the rotation amount of the first rotating body is specified according to the specified rotation angle of the first rotating body and the rotation speed of the first rotating body.

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